Commercial shrimp and aquaculture farms suffer extensive losses due to the effects of a number of common pathogens. Vibrio harveyi, a Gram-negative, rod-shaped bacterium, is reported to be the most important bacterial pathogen of the worldwide shrimp aquaculture industry. Some strains of this bacterium are highly pathogenic to shrimp, while other strains may be considered to be opportunistic pathogens.
Detection of Vibrio harveyi in hatchery broodstock and in post-larvae allows infected shrimp to be eliminated before entry into a commercial production system. Consequently, a variety of methods have been developed for the detection of Vibrio harveyi in shrimp, including nucleic acid-based methods and immunological methods (Lightner et al., Aquaculture 164(1):201-220 (1998)). Polymerase chain reaction (PCR) methods are of particular interest because they are simple, rapid, and sensitive. PCR methods for the detection of Vibrio harveyi, which are based on amplifying different diagnostic regions of the genome, have been described (see for example, Conejero et al., J. Gen. Appl. Microbiol. 50(3):137-142 (2004); Conejero et al., J. Appl. Microbiol. 95(3):602-611 (2003); and Oakey et al., J. Appl. Microbiol. 95:1293-1303 (2003)).
All of the above methods are useful for the detection of Vibrio harveyi; however, they generally suffer from a lack of specificity, sensitivity, or are complex and time consuming. Additionally, because of the high gene mutation rate in the bacterium, tests directed to different regions of the genome would be useful. Therefore, there is a need for a highly sensitive assay for Vibrio harveyi that is rapid, accurate and easily used in the field. The stated problem is addressed herein by the discovery of primers based on a portion of the Vibrio harveyi LuxR gene that may be used in primer directed amplification or nucleic acid hybridization assay methods for the detection of Vibrio harveyi without the problems associated with previous methodologies.